Parallel Three-phase Research Articles

Postprandial effects of macronutrient composition meals on the metabolic responses and arterial stiffness indices of lean and obese male adults: a protocol of a pilot study

BackgroundPrior studies have shown that meal composition may affect the metabolic responses and arterial stiffness indices, and these responses may be different in lean and obese adults. The primary objective of this study is to determine the feasibility of conducting a trial to compare the effect of three test meals in lean and obese men. Due to the lack of a comprehensive study that concurrently compares metabolic responses and vascular stiffness indices after receiving three different meals in lean and obese men, this pilot study will be conducted with a three-phase parallel design, aiming to investigate the effects of meal composition on the metabolic parameters and arterial stiffness indices of lean and obese adults.MethodsThis pilot, a parallel clinical trial will be performed on 24 male adults aged 18–35 years since January 2021 and will continue until March 2021 who are disease-free and selected based on the inclusion and exclusion criteria at Mashhad University of Medical Sciences, Iran. The subjects will complete three interventions at a 1-week interval, including high carbohydrate (70% carbohydrates, 10% protein, 20% fat), high protein (30% protein, 50% carbohydrates, 20% fat), and high-fat meal (50% fat, 40% carbohydrates, 10% protein). Postprandial effects will be assessed within 360 min after each meal, including the energy expenditure component (resting energy expenditure, thermic effects of feeding, respiratory quotient, and substrate oxidation) and arterial stiffness indices (augmentation index and pulse wave velocity). In addition, blood sampling will be performed to measure glucose, insulin, free fatty acids, and lipid profile.DiscussionThe differences in the postprandial responses can affect the metabolic and vascular parameters due to different meal compositions, thereby providing beneficial data for the establishment of new strategies in terms of nutritional education and metabolic/vascular improvement. Also, the results from this pilot study will inform intervention refinement and efficacy testing of the intervention in a larger randomized controlled trial.Trial registrationIranian Registry of Clinical Trials; code: IRCT20190818044552N1; registered on August 26, 2019

The d and q Axes Technique for Suppression Zero-Sequence Circulating Current in Directly Parallel Three-Phase PWM Converters

The directly parallel pulse width modulated converter (DPC) method is used to construct large-scale converter systems to increase system performance and reduce costs. However, circulating currents arise when the converters supply unbalanced currents or have different converter parameters. Circulating currents cause distortions in the current, increase the current coming from each converter, and degrade the system performance. This paper proposes a circulating current control (CCC) methodology to eliminate circulating currents through the analysis and approximation of the circulating current of the fundamental harmonic current at 150 Hz. By using the phase shift technique, this new model of the circulating current in the 0 -axis was extended to the $0d$ - and $0q$ -axes. The proposed CCC was then designed according to the new circulating current model and added to the conventional controller. The performance of the proposed CCC converter was verified via simulation and experimentally with three directly parallel 5.5 kVA converters. The proposed CCC enhanced controller and conventional controller were tested with various current values, and all resulting circulating currents were recorded. The experimental results showed that the proposed CCC eliminated nearly all the circulating currents and that it had a fast, dynamic response to step-change currents. Using ramp current sharing, the experimental results were confirmed. Additionally, the efficiency of the proposed CCC in the DPC was significantly higher than the conventional controller, and the system’s efficiency was the same as that of a single converter connection. Thus, using the proposed CCC in DPC systems is economical, highly efficient, modular, and flexible.

Grid Harmonic Current Correction Based on Parallel Three-Phase Shunt Active Power Filter

This article presents a finite-set model predictive control (FS-MPC) applied to the shunt active power filters (SAPF) based on three-phase inverters connected in parallel sharing the same dc-link. The discrete-time model of the system is used to predict the future value of the grid, circulation, and offset currents. The presence of circulation and offset currents occurs due to the connection of the two inverters in parallel sharing the same dc-link. There are 64 switching state vectors for SAPF and, in order to reduce the burden of calculation, only 30 switching states are chosen and applied, however keeping the advantages of the FS-MPC algorithm. The control strategy ensures the sinusoidal shape of the grid current, high power factor, and circulating and offset currents suppression. The FS-MPC has its performance compared to the pulsewidth modulation (PWM) strategy considering the SAPF with two parallel inverters, the conventional SAPF and the neutral-point-clamped SAPF. These comparisons include harmonic distortion, power semiconductor losses, and analysis of dc-link capacitor losses. As a multilevel topology, the SAPF with two parallel inverters using FS-MPC present competitive efficiency and can be applied with a good performance in industrial and residential applications. Simulation results and a laboratory-scale experimental platform is used for corroborating the proposal.

Performing reactive power compensation of three-phase induction motor by using parallel active power filter

Nowadays, the problem of power quality increases day by day. Harmonic current and reactive power are the important factors disturbing the power quality. The induction motors draw both harmonic current and reactive power from the grid. Reactive power and harmonic current lead to heat losses and decrease in the efficiency of the transmission lines. Passive and active filter applications have been used to solve these problems. There are some disadvantages of passive filters. Large physical dimensions and resonance with load can be shown as examples for these disadvantages. Therefore, the application areas of Active Power Filter (APF) are rapidly developing due to the fact that they can be applied together with harmonic and reactive power compensation as appropriate control methods. This paper proposes a MATLAB/Simulink simulation to perform power factor correction and reactive power compensation of three-phase induction motor by using three-phase Parallel Active Power Filter (PAPF). In order to generate PAPF’s reference currents the Sine Multiplication Technique (SMT) is used. Simulation studies are presented to be able to assess the performances under different motor operating conditions. The proposed hysteresis controller based PAPF filter makes the power factor up to 1 and the reactive power compensation of the three-phase induction motor.

Multistep finite-control-set model predictive control of active power filter

The traditional finite-control-set model predictive control (FCS-MPC) of three-phase active power filter (APF) has the problems of low compensation precision and long control delay. In order to address this problem, this paper proposes a multistep prediction compensation control method for the FCS-MPC of APF, it does not require modulation of PWM link. By utilizing the discrete mathematic model of three-phase parallel APF and keeping the advantages of traditional FCS-MPC, the prediction model is established based on the structural model of traditional FCS-MPC, the predictive controller is designed for predictive control of DC-side voltage. AC-side current and fixed switching frequency, and simulation study is also conducted. The simulation results show that the multi-step predictive control method can effectively track and compensate harmonic, reduce the harmonic component of power grid, and increase the compensation precision of parallel APF.

Advanced Synchronization Control for Inverters Parallel Operation in Microgrids Using Coupled Hopf Oscillators

A simple high-performance decentralized controller based on Hopf oscillator is proposed for three-phase parallel voltage source inverter (VSI) in islanded Microgrid. In αβ frame, the oscillators equations corresponding output current and common bus voltage as feedbacks are designed according to coupled oscillator synchronization properties. The enough common bus information is considered to realize external synchronization, and the current feedback is to achieve internal synchronization between VSIs. Then, the controller employs Hopf evolution dynamics to integrate their both. Therefore, a larger phase error can be eliminated when additional inverter connects, and the pre-synchronization item is proposed to be close to synchronize with the operational inverters. In addition, an integrated small-signal states pace based on averaged model for two parallel VSIs is developed, and the root locus shows the large stability margin and low sensitivity of parameters. Simulation and experiment results verified the effectiveness of the proposed method in aspects of the fast dynamics response and precise current sharing performance.

Research on Parallel Control Technology of Three-phase Inverter Based on Multiple Proportional Resonance Controller

The parallel operation of multiple inverters can increase the fault tolerance of the system and prevent the occurrence of major accidents. At the same time, it also has strong flexibility, which can reduce the volume and weight of the system and increase the capacity of the system, which is very attractive in the application of uninterruptible power supply. In the inverter parallel system, the circulation will be generated between the inverters due to the existence of the path. Circulation can cause current distortion, reduce system performance, and even damage equipment in severe cases. In order to effectively suppress the generation of circulation, this paper proposes a multiple proportional resonance control strategy for the parallel three-phase inverter system, that is, the voltage outer loop is controlled by PI+PR, and the current inner loop is controlled by PR. Two three-phase inverter parallel systems are built in MATLAB/Simulink simulation environment to compare and analyze the control effect of uncontrolled, traditional PI control and multiple PR control. The simulation results show that the proposed control method has a good suppression effect on the circulation generated in the inverter parallel system, even under the condition of unbalanced load.

Robust Power Sharing Control for Parallel Three-phase Inverters Against Voltage Measurement Errors

In islanded microgrids, distributed generations (DGs) have been increasingly employed through parallel voltage source inverters (VSIs). To fully utilize the VSI capacity and avoid overloading, the total load power is expected to be accurately shared among VSIs based on their power ratings. However, it is revealed that even small voltage measurement scaling errors may severely deteriorate the power sharing by injecting positive- and negative-sequence circulating currents. An explicit analysis indicates that this issue cannot be avoided if the conventional voltage-feedback control is adopted with an accurate fundamental voltage tracking ability. To solve this problem, a hybrid feedback and feedforward control is proposed, which makes the power sharing robust against voltage measurement errors. In specific, the feedforward control is utilized to enhance the unbalanced and reactive power sharing by reshaping the VSI fundamental output impedance. Meanwhile, the feedback-based impedance shaping control is also employed to improve the harmonic power sharing. As no communication and sensor error knowledge are required, the proposed control scheme provides a simple but effective solution for decentralized power sharing among parallel three-phase VSIs. Finally, both simulation and experimental results are provided for verification.

Simulation and analysis of three-phase parallel inverter using multicarrier PWM control schemes

Simulation and analysis of three-phase parallel inverter using multicarrier pulse width modulation such as phase disposition (PD), phase opposition disposition (POD) and alternate phase alternate disposition (APOD) are presented in this article. In this proposed work, reduced active switching count, transformers, single DC input, a high degree of modularity and redundancy are key merits and also suitable for renewable energy systems. The proposed three-phase five-level multilevel inverter with single DC source using a three-phase transformer is controlled by multicarrier pulse width modulation schemes. To generate switching pulses for five-level inverter, four carrier signals can be compared with a reference signal. The performance of the inverter is examined by using PD, POD, and APOD by modulation index (MI) starting from 0.4 to 1. Furthermore, the over-modulation region is also analyzed in this paper. The effectiveness of the system is analyzed in terms of total harmonic distortion by varying the MI of the inverter. The simulation results are verified through MATLAB/Simulink.

Analysis of Three-Phase Inverter Parallel Operation with Network-Based Control Having Strong Robustness and Wide Time-Scale Compatibility in Droop-Controlled AC Microgrid

The system performances can be potentially enhanced for three-phase inverter parallel operation in droop-controlled AC microgrid by using network-based control, which also benefits for the extension of other control strategies in microgrids (MGs). It is highlighted that some negative factors such as network-induced time-delays and data dropouts would possibly degrade the system operation. In this paper, the comprehensive analysis of network-based control strategy with strong robustness and wide time-scale compatibility is investigated in islanded mode of an AC microgrid with paralleled inverters. The theoretical evaluation towards time-delay and data dropouts is made and it is verified that its good power-sharing can be obtained under unsatisfactory communication conditions. It has been observed that the time-scale of network-based control can also be designed from several microseconds to milliseconds. Based on this idea, the communication integration of different layers of MGs in hierarchical structure would be realistic. Experimental results have verified the effectiveness of the network-based control strategy and analytical method.

Functioning ability of multilevel Vienna converter as new parallel active filtering configuration: simulation and experimental evaluation

This paper presents a modern solution based on power electronics, recommended to solve the problems posed by harmonic pollution of the electrical network. This pollution is generated mainly by nonlinear loads such as rectifiers with diodes and thyristors, recognized as the principal source of harmonic currents injection. As such, a curative solution was provided by a new three-phase parallel active filter based on the multilevel Vienna converter. The novel task assigned to the Vienna converter is to compensate the reactive power and to eliminate the harmonic currents caused by the nonlinear polluting loads. A simple and effective control approach has been developed guaranteeing sinusoidal shape source currents and unity power factor of the electrical network. In addition, the multilevel Vienna converter-based parallel active filter operates with convincing performances identified through the admitted DC output voltage undulations and the balance between the two partial outputs voltages. Satisfactory results have been obtained when the proposed algorithm has been subjected to simulation using the MATLAB/Simulink software and confirmed in real-time implementation via a dSPACE 1104 card.

Analysis of the unbalanced harmonic propagation in a three-phase power system using a parallel program

Operation of non-linear in an unbalance condition can cause harmonic problems in the power system. There are two parts in the use of computing time in harmonic load flow, the first in the construction of harmonic admittance matrix and the second is the iteration scheme for solving systems of linear equations. The solution technique of the harmonic admittance was developed as a parallel application, and a direct algorithm to calculate the admittance matrix elements. The three-phase power flow program is devided into three independent subproblems, namely: positive, negative, and zero sequence network. Positive sequence network had been been solved by using the Newton Raphson method without modifying their formulation. Negative and zero sequence networks had been solved using nodal voltage equation. All three sequence networks have been modeled by three independent circuits and solved simultaneously using multi-core processors in parallel programming. The results showed that the parallel three-phase load flow speed is higher than the sequential.

Parallel Operation of Unity Power Factor Rectifier for PMSG Wind Turbine System

Offshore wind power has inspired the fields of high voltage direct current (HVdc) for advantages of high power transmission in long distance. Hefty wind generators are making advanced multilevel rectifier and parallel operation of rectifiers popular choice of research with the aim to accommodate higher power. Issues of reliability and complexity of control are associated with active power electronic devices at such high power. This paper focuses on the novelty of operation of parallel three-phase diode rectifiers each with auxiliary bidirectional switching blocks (BSB) to improve their performance. For the system, maximum percentage power is commuted through the three-phase diode rectifier and paralleling further lessens the current stress on the semiconductor switches present in the BSBs. Competence of continuous operation at times of any specific branch failure provides the proposed system with higher modularity and reliability. The paralleled topology is controlled to obtain unity power factor at the generator output with low generator output-current harmonics using hysteresis current control. The dc-link voltage is controlled at a reference value, for various dynamic variations along with balanced capacitor voltages. The permanence of the proposed system is simulated for scenarios associated with variation of wind speed and load demands while various operation modes are tested on a 2.5-kW experimental setup.

Investigation of Zero Sequence Circulating Current Suppression for Parallel Three-Phase Grid-Connected Converters Without Communication

The parallel three-phase grid-connected converters (GCCs) with common dc and ac buses can increase the system power level effectively. However, zero sequence circulating current (ZSCC) will occur inevitably. In this paper, the mechanisms and characteristics of ZSCC in two parallel three-phase GCCs are first investigated based on three typical cases. From the analysis, it was found that not all ZSCC can be suppressed. Generally speaking, ZSCC caused by inconsistent modulation voltages between modules cannot be effectively handled. And ZSCC caused by different injected zero sequence voltages (ZSVs) or asynchronous carriers can be suppressed. Based on the theoretical analysis, identical ZSV injection and carrier synchronization methods without communication are, thus, proposed to suppress ZSCC at the source, which are easily implemented without adding any hardware. Finally, the theoretical analysis and the effectiveness of the proposed methods on ZSCC suppression are well-verified by experiments.

A Decentralized Coordination Control Method for Parallel Bidirectional Power Converters in a Hybrid AC–DC Microgrid

In the hybrid ac–dc microgrid, the ac and dc subgrids are connected by bidirectional power converters (BPCs) that play an important role in the load power sharing and power interaction between the ac and dc subgrids. The coordination control and circulating current suppression for the parallel BPC system are very challenging. In this paper, a decentralized coordination control method is proposed for parallel three-phase BPCs, which can suppress the circulating currents, realize proper power interaction, and achieve overall load power sharing in both the grid-connected mode and the islanded mode. The performance of the proposed control methods is verified by the real-time hardware-in-loop tests.

Suppression of Zero Sequence Circulating Current for Parallel Three-Phase Grid-Connected Converters Using Hybrid Modulation Strategy

The parallel three-phase grid-connected converters sharing dc and ac bus can increase the system power level effectively. However, the zero sequence circulating current (ZSCC) will occur inevitably under space vector pulse width modulation or discontinuous pulse width modulation (DPWM). In this paper, the mechanism and the mathematical model of ZSCC are studied. Then, a hybrid PWM (HPWM) strategy is proposed to suppress the ZSCC based on the same zero sequence voltage injected, which is dependent on the common grid information. The dc voltage utilization of HPWM can be extended compared with sinusoidal PWM (SPWM). The number of parallel modules can be infinity theoretically by using HPWM. It is noted that there is no internal commutation among modules (expect the dq current reference). Finally, the feasibility and the effectiveness of the proposed method are verified by experiments.

Analyzing and Designing a Current Controller for Circulating Current Reduction in Parallel Three-Phase Voltage-Source Inverters

A circulating current is a major problem caused by directly connecting voltage-source inverters (VSIs) in parallel. This circulating current occurs as a zero-sequence current between the inverters by specific switch states. Several studies have presented alternatives using hardware and software methods. When coupled inductors (CIs) are employed for the high-frequency circulating current, a controller is required to prevent the low-frequency circulating current from saturating the CIs. In this study, the zero-sequence circulating current and its alternatives are investigated using hardware and mathematical description. A high-performance circulating current controller is proposed by applying a repetitive controller to the zero-sequence current control loop. The proposed controller can effectively minimize the low-frequency circulating current without any data sharing between the inverters in unfavorable conditions. It can also be applicable to the modular configuration of parallel three-phase VSIs. Experimental results verify the performance of the proposed controller.

Parallel Three-Phase Interfacing Converters Operation Under Unbalanced Voltage in Hybrid AC/DC Microgrid

Parallel interfacing converters (IFCs) with the same dc link are commonly used to handle higher power and currents. In hybrid AC/DC microgrids, they are used to connect ac and dc subsystems, called interlinking IFCs. However, researches on parallel IFCs under unbalanced voltage are quite limited. Considering the adverse effects of unbalanced voltage on a single IFC operation (such as output power oscillations, dc link ripples, and output current increase) and the possibility of aggregation of these effects for the parallel IFCs with common dc link, a novel control strategy for parallel IFCs with various power factors is proposed in this paper. The proposed control strategy cancels out active power oscillation of parallel IFCs, which results in oscillation-free dc link/subsystem voltage. In this paper, a thorough study on the peak current of individual and parallel IFCs is conducted, and their relationship with active power oscillation mitigation is analyzed. Based on analysis, it is proven that under zero active power oscillation, the collective peak current of parallel IFCs is constant under fixed average active and reactive powers. The proposed control strategy keeps the individual IFCs’ peak currents in the same phase with collective peak current of parallel IFCs, and thus ensures reduced peak current for redundant IFC.

Review of the most applicable regulator collections to control the Parallel Active Power Filter

<p class="Abstract">This work presents a study of the three-phase parallel active power filter and the various controllers used in its control. Moreover, in order to improve the quality of electrical energy, by making it conform to the new normative constraints, we have also been led to develop and apply advanced automation methods. In this framework, this paper reports of several regulatory structures : fuzzy logic, PWM, new space vector PWM (NSVPWM), space vector PWM (SVPWM), HYSTERESIS moreover, in order to produce a parallel active filter, a thorough study of experimental feasibility was carried out, taking into account the industrial constraints of the product both in its design and its application.</p>

Review of the most applicable regulator collections to control the Parallel Active Power Filter

This work presents a study of the three-phase parallel active power filter and the various controllers used in its control. Moreover, in order to improve the quality of electrical energy, by making it conform to the new normative constraints, we have also been led to develop and apply advanced automation methods. In this framework, this paper reports of several regulatory structures : fuzzy logic, PWM, new space vector PWM (NSVPWM), space vector PWM (SVPWM), HYSTERESIS moreover, in order to produce a parallel active filter, a thorough study of experimental feasibility was carried out, taking into account the industrial constraints of the product both in its design and its application.